Magneto timing tool



Oct. 4., 1960 c. J. BIGOS MAGNE'I'O TIMING TOOL Filed Aug. 4, 1958 INVENTOR. CHESTER J. Bl G03 ATTORNEYS MAGNETO TIMING TooL Chester J. Bigos, Box 54, Phoneton, Ohio Filed Aug. 4, 1958, Ser. No. 752,688 1 Claim. cl. 18869) This invention relates to a tool for use with a magneto to hold the distributor gears and magneto shaft in timed operating relationship while the magneto is assembled with an engine.

Propereconomical operation of spark ignition internal combustion engines using a magneto in the ignition system is dependent upon the application of a spark of Proper intensity from the engine magneto to each of the spark plugs within the various cylinders at the times when the pistons are each located in firing position. Premature or delayed firing resulting from improper timing of the magneto distributor results in loss of engine power and in some instances, for example in aircraft engines, renders the engine unusable for practical purposes until retiming can be undertaken. Also, if the magneto generator is out of time, the generated electrical potential may not reach a maximum at the time a cylinder is firing and substandard engine power can result. One problem encountered in achieving proper timing is the diffiwhy in mounting the magneto in operating position on the engine after it has been internally timed, since it is difficult in many instances to connect the magneto shaft to the engine without rotating it accidentally enough to throw the magneto out of time. i a

Therefore, it is a principal object of this invention to provide a tool for engaging the teeth of a magneto distributor 'gear to prevent any accidental turning of the magneto shaft or distributor gears while installing the magneto on an engine. 7

Another object of this invention is to provide a tool which can be fastened to the casing of a magneto and adjusted radially with respect to the axis of the distributor gear to lock the gear in adjusted or timed position and keep the magneto shaft from turning.

Other objects and advantages of this invention will be apparent from the following description, the accompanying drawings and the appended claim.

In the drawings.

Fig. 1 is' a front elevation of the magneto having a portion of the casing removed and the tool of the present invention shown in operating position;

Fig. 2 is a fragmentary view showing the magneto breaker points and the point operating cam attached to the magneto shaft;

Fig. 3, is an exploded perspective of certain of the magneto parts showing the rotating magnet mounted on the magneto shaft; 7

Fig. 4 is a vertical section through the tool of the present invention;

Fig. 5 is a side elevation of the tool showing the manner in which it is inserted through the timing opening of the magneto casing;

Fig. 6 is a somewhat enlarged view, in part sectional and in part full, of the apparatus secured to the magneto housing with the locking member out of engagement with the distributor gear; and

Fig. 7 is a fragmentary view showing the manner in which the foot portion of the locking member engages a tooth of the distributor gear to prevent it from turning in either direction.

Referring to Fig. 1 of the drawing, a magneto of the type with which the tool of the present invention may be used includes a casing 10, which is made up of an outer part 11 and an inner part 12. The part 11 has a timing and inspection opening 13 in its upper wall and part 12' includes a slotted mounting ear 14 on each side thereof, only one of these ears being shown, for receiving mounting bolts in mounting the magneto on an engine, while providing for limited angular adjustment to facilitate mounting on the engine. The angular adjustment also enables the magneto to be turned to compensate for any back lash or free play which may be present in the driving gears within the engine.

A relatively large distributor gear 20 is mounted for rotation with a shaft 21, which may have a rotor arm or equivalent element mounted thereon to eflect sequenced firing of the spark plugs which are electrically connected to the distributor portion of the magneto. A second, and relatively smaller, distributor gear 25 is mounted on a magneto shaft 26 and in meshed relationship with gear 20 so that rotation of shaft 26 will cause corresponding rotation of shaft 21. The magneto shaft 26 carries a magnet 27 which is rotated within a field winding (not shown), but which would be carried by core pieces 28 in the usual manner, to generate electrical pulses in the usual manner for use in firing the engine, the magnet being secured on the shaft and enclosed within part 12 of the casing. The other end of shaft 26 is enclosed completely by the casing part 11 and has a cam 36 secured for rotation in contact against insulating disk 31 which is in turn secured to the casing part 11 through spring arm 32 and the mounting plate 33. The mounting plate 33 carries a set of breaker points 35, one of which is mounted on a spring arm 36 for movement toward and away from the other point when the high point of cam 30 contacts the fiber disk 31, moving it toward arm 36. A grounding spring 37 extends between casing part 12 and resilient arm 36 to complete the electrical circuit.

In the magneto described, the internal timing is im portant to assure that the flux density of magnet 27 is at its peak, and that therefore the current is at a peak, when the points break, so that maximum voltage can be delivered to the spark plugs. If the breaker points 35 are adjusted to a given clearance without considering internal timing it is possible for the points to open before or after the peak fiux density has been reached, thereby lowering the voltage output to the spark plugs below the maximum obtainable voltage. The internal timing relates to the relationship between distributor gears 20 and 25 with respect to the direction of rotation of the engine, this diiference in engine operation being provided for by the marks labelled L and R on the distributor gear 2% and the single mark 38 on the smaller distributor gear 25. To place the magneto in internally timed relationship, the large distributor gear 20 is removed from the casing 10 and turned until one or the other of the marks L and R is in alignment with the mark 38, depending upon the direction in which it will be driven by the engine. With the internal timing marks in alignment, the breaker points 35 are then adjusted so that they just begin to open, and the magneto and engine ignition is then timed properly.

The larger distributor gear 20 carries a third timing Fatented Get. 4, 1960 r 3 mark, indicated by the numeral 40, which is located directly diametrically opposite a point exactly midway between the internal timing marks L and R, and this mark is for use in achieving external timing of the magneto. This particular correlation between the mark 44) and the marks L and R, is used in determining from outside the casing the proper position of the distributor gear when installing the magneto as well as in checking the point setting of an assembled magneto. Once a magneto has been internally timed, that timing will normally not change, however the external timing may vary, for

example due to wearing of the breaker points, and inspection and adjustment may be made periodically to achieve maximum operating efiiciency from the magneto. The inspection and timing opening 13 provides means to observe the location of timing mark 40 and therefore the location of magnet 27.

' One of the problems encountered in obtaining a properly timed engine is the difiiculty in assembling the magneto to the engine without upsetting the external timing through accidental movement of the magneto shaft 26. After the magneto is timed internally and externally, the crank shaft of the engine should be turned to the correct position before top center on the compression stroke of number 1 cylinder, according to standard practice. The magneto must then be operably connected to the engine, by means of a conventional dogclutch or similar driving connection (not shown), for operation to fire the various spark plugs at the correct times.

Since the magneto shaft 26 is freely rotatable it is a difiicult matter to connect the magneto to the engine without destroying the timing. Additionally, the driving gears to which the magneto is connected often have enough back lash to throw the magneto enough out of time to make considerable difference in the amount of voltage developed by the magneto during the firing periods. The tool of the present invention is designed to beattached to casing 10 for engagement with one of the distributor gears and thereby hold all of the various rotating parts against accidental rotation. When the tool is assembled in position, as shown in Fig. 1, the magneto can be worked into position on an engine without any fear of accidentally upsetting'the timing of the apparatus. Additionally, once the magneto is operably connected to the engine the entire magneto can be rotated until the gears are tight, this feature enabling the back lash to be removed from the gears and insure precise timing;

Referring to Fig. 6, the tool comprises a locking ,mem-

ber 45 which includes arod-like elongated shank portion 46 which can be inserted .through timing opening 13 into the interior of casing 10. .One .end of the shank portion 46 has a foot portion 47 secured thereto by a transversely extending pin 48, the foot portion .having a recess 49 in the lower surface thereof forming a pair of side members fitt. The groove 491s suitably dimensioned to receive one of the teeth formed on the outer edge of gear 20 and thereby hold the gear against accidental rotation.

A fastening device '55 is mounted on shank portion 46 above foot 47 and has axial bore 56 extending completely therethrough for reception of the shank portion 46. Fastening device includes ,a central, enlarged body portion 57 having a roughened outer surface for grasping by an operator. An extension 53, having external screw threads 59, extends from one side of central body portion 57 for securing fastening device 55 to casing 10 as shown in Figs. 1, 4 and 6. A second, externally threaded extension oii protrudes from the opposite side of central body 5'? and contains a pair of diametrically opposed,

4 and force the extension into frictional engagement with the outer wall.

Member 63 is slidably mounted on shankportion 46 and has an internally threaded web portion on one side thereof to mate with the external threads on extension 69. An upper web portion on the other side of member 63 has a sloping surface 64 complementary to surface 62 and adapted to abut thereagainst when the member 63 is threaded down onto extension 60. By threading the device 63 far enough onto extension 60, the surfaces 62 and 64 will contact and the radial component of force created will urge the separate halves of extension 60 inwardly against shank portion 46 to prevent vertical movement of the locking member '45. When the fastening member 63 is loos'e the locking member 45 can be axially adjusted to project foot portion 47 into engagement with distributor gears of varying diametersl For example in Fig. 6 the foot portion 47 is shown out of engagement with gear 13 whereas in Figs. 1 and 7 it is shown in looking engagement with a gear tooth on thegear 20. A snap ring 65 is secured to the opposite end of shank portion 46 from foot 47 to prevent the fastening device 55 and fastening member 63 from slipping off the end and possibly becoming lost. 7

Fig. 5 illustrates the manner in which the locking member 45 is inserted through the timing opening 13 into the interior of casing 10 for engagement with a tooth on gear 20 by tilting it slightly as it is inserted. The fastening device 45 and the fastening member 63 are shown completely separated on the locking member 45, although in actual practice it should be possible in most instances to leave member 63 threaded loosely on device .55 rather than completely separating the two members to vertically adjust member 45.

With the present tool assembled in operating position on the magneto, the gear 20 and the other related parts,

precise form of apparatus and that changes may be made thereinwithout departing from the scope of the invention which is defined in the appended claim.

Whatis claimed is:

A retaining tool adapted forv temporary attachment to a magneto to maintain the movable parts thereof in predetermined fixed relation during installation of the magneto on an engine, comprising an outer supporting tool body having an extended through bore providing a supporting bearing surface of substantial length, an externally threaded lower end on said body of reduced crosssection providing a shoulder adapted for fixed seating in temporary mounted position on the casing of the magneto with said externally threaded lower end received in a threaded inspection opening of said magneto, an elongated externally threaded upper end on said body terminating in a tapered end portion, said upper end having a slot essentially the full length thereof and extending laterally through said upper end from said bore to the exterior of said body providing for radial contraction of said upper end, a fastening member threaded about said upper end and having an internal tapered surface complementary to said tapered end portion for cooperation therewith to exert a contracting force on said upper end portion, a locking rod slidably received in said bore in contact with substantially the entire said supporting bearing surface and extending beyond both said upper and lower ends of said body, and a grooved foot rigidly securedto the end of said rod beyond said-lower end and adapted to engage a timing gear within the magneto to lock the gear in predetermined fixed position, said rod being movable through said bore to engage said foot portion securely with a timing gear and said fastening member cooperating with said slotted upper end to clamp said rod in an infinite number of adjusted positions to accommodate variable spacing between the timing gears of different magnetos and the inspection openings therein.

References Cited in the file of this patent UNITED STATES PATENTS Knapp Sept. 20, 1921 Pelsue Dec. 19, 1922 Smith July 20, 1926 Gross May 9, 1944 Marlow Mar. 5, 1946 

